Calibre 633 was a member of the Jaeger-LeCoultre Mechaquartz family. It was the most complicated movement in the family, with 27 jewels and an alarm function.
There are two motors in the calibre:
- One powers the main timekeeping hands at a frequency of 1 Hz
- A second powers the mechanical chronograph at 4 Hz
Since the chronograph is mechanical, it has the same feel as a conventional chronograph movement, including mechanical zero reset. Yet the Mechaquartz was much more compact than a conventional automatic chronograph movement.
Calibre 633 differed from Calibre 630 and 631 in that it included an alarm function.
Note: There is conflicting information on the quartz frequency, with some sources claiming dual 1 KHz and 4 KHz crystals and others claiming 32 KHz.
Calibre 633 was used in chronograph watches in the 1980's and 1990's, though not as widely as Calibre 631: